Software Defined Radio (SDR) and Field Programmable Gate Array (FPGA) devices are technologies which allow enormous flexibility in the design of communications components and systems.
Despite the widespread availability of these technologies, they have not been systematically integrated into telemetry system design processes to increase efficiency and reduce cost associated with customizing telemetry systems.
For example, a transponder for a NASA communication system costs more than $500,000. There is currently a need to reconfigure countless hardware components for a specific telemetry application.
Software Defined Radio (SDR) is a term used to refer to technologies which minimizes the amount of analog and radio frequency components needed to convert radio frequencies into digital frequencies. The SDR concept and principles of design use a minimum amount of analog/Radio Frequency components to up/down-convert the RF signal to/from a digital format. Once analog signals are converted to digital signals, all other processing (filtering, modulation, demodulation, etc.) can be done in software rather than with hardware.
A field programmable gate array (FPGA) is an integrated circuit designed to be configured by a user after manufacturing and is a simplified and economical alternative to an application specific integrated circuit (ASIC). In theory, an FPGA can be used to implement any logical function that an ASIC can perform. For example, a user can embed various programming languages, processing functions and FEC error checking protocols into an FPGA.
Error checking protocols are critical to all telemetry systems. Error detection, correction and control enable reliable delivery of digital data over unreliable communication channels without requiring retransmission of data. Error detection techniques allow detecting such errors, while error correction enables reconstruction of the original data.
Error checking protocols are used for both uplink and downlink communications. FEC protocols, in a particular are used for controlling errors over unreliable communication channels.
There are several protocols for telemetry systems that comply with standards developed by the Consultative Committee for Space Data Systems (CCSDS), and which may be used in conjunction for specific telemetry applications. Examples of CCSDS protocols related to telemetry include Reed-Solomon (forward error correction), ASIC BCH (error detection), and Pseudo-Randomization (required for synchronization). These protocols are typically programmed onto microchips and embedded processors that are combined into telemetry systems. Each FEC or detection code may be considered an intellectual property (IP) block that can be added or removed from the design to support mission requirements using proven IP.
There is an unmet need for an optimized telemetry transponder device and system that utilizes the efficiencies and flexibility of SDR and FPGA technology to meet all of NASA's telemetry needs and minimize the cost of expensive reconfiguration.
There is a further unmet need for telemetry systems which can be modularly reconfigured with various CCSDS compliant error checking protocols to accommodate diverse telemetry systems without requiring a complete redesign of a transponder.